Spinal stenosis is a pathology of the spine that involves the narrowing of the spinal canal, through which the spinal cord and nerve roots run. This narrowing may be congenital and, consequently, can affect patients at any age. Spinal stenosis may result from thickening and calcification of spinal ligaments. For example, calcification can result from deposits of calcium salts within the spine. In addition, spinal stenosis can result when bones and joints are enlarged, leading to the formation of osteophytes (bone spurs). A significant cause of osteophytes is spondylosis, in which spinal discs lose water and become less dense. Also, a bulging or herniated disc may place pressure on the spinal cord or nerve root such that the area of the spinal canal is reduced. Finally, diseased bone or tumors can extend into the spinal cord area, decreasing the space available for nerve roots within the spinal canal.
Compression of the spinal cord resulting from spinal stenosis can produce pain, weakness, or loss of feeling in the patient. Additionally, spinal cord compression can lead to myelopathy, which causes neurological damage and results in spinal cord malfunction. If left untreated, the compression can eventually damage the circulatory system within the spinal cord, leading to more severe myelopathy.
Two surgical methods are traditionally used to decompress the spinal cord from a posterior approach to the spine. First, the laminectomy involves the removal of the lamina and spinous processes in order to expose the dura covering the spinal cord. Due to the removal of portions of the supporting structures at the posterior of the vertebra that are used to align the spinal column, a laminectomy can create postural deformities in patients. In addition, there is a risk that the procedure will lead to substantial scar formation in the patient. In order to address these concerns, a graft may be installed between the vertebral bones involved to promote fusion. However, this may lead to a decrease in the range of motion in the spine, and there may also be accelerated degeneration of the vertebrae above and below the repaired vertebra.
The second method traditionally used to decompress the spinal cord is the laminoplasty. In a laminoplasty procedure, the targeted vertebra is cut and the lamina repositioned so that the lamina is lifted off the dura and the spinal canal is thus enlarged. Then, a plate and/or a graft are inserted to permanently enlarge the spinal canal. There are generally two techniques used to perform a laminoplasty. First, the unilateral or “open door” laminoplasty involves cutting entirely through a first portion of the lamina on the first side of midline of the targeted vertebra, while a second portion of the lamina on the second side of midline is only cut partially through to create a hinge. Then, the first lamina portion is hinged away from the spinal cord to increase the size of the spinal canal. Finally, a graft and/or plate is inserted into the opening to permanently enlarge the spinal canal. Second, the bilateral or “French door” laminoplasty involves cutting entirely through the midline of the spinous process, and then cutting partially through both sides of the lamina portion, creating two hinges. The vertebra can then be opened at the bisected spinous process, and a graft or plate can be inserted into the opening to permanently enlarge the spinal canal.
Unlike the laminectomy, the laminoplasty does not involve the excising of any bone material. In addition, when compared to the laminectomy, the laminoplasty may provide greater stability. A wider range of motion for the patient is maintained compared to a fusion. Through the use of laminar fusion and fixation techniques in a laminoplasty procedure, the achieved decompression and position of the displaced lamina can be more effectively maintained.
Despite the advances that have been achieved in laminoplasty procedures, there are still some limitations in the effectiveness of the procedures and the ease with which the procedures are completed, especially when performed on the cervical vertebrae. For example, the present technique requires the surgeon to make a large incision to reach the spine, which includes stripping of muscle and ligament attachments to the bone, and this can lead to significant muscle and tissue damage. In addition, in cervical spine surgeries, the smaller size of the target vertebra makes the operation more complicated. For instance, the surgeon may find it difficult to make precise adjustments within the operating space or to know whether the lamina has been displaced an appropriate distance. Further, in some patients, the increase in area that can be achieved by current techniques is insufficient to provide complete relief from spinal cord compression. Finally, due to the uneven nature of “open door” laminaplasties, patients may have a slight imbalance in their spines following the procedure, and the increase in spinal canal diameter is asymmetric.
Similarly, the laminoplasty plates that are currently used also have limitations. For example, many current laminoplasty plates are too large in size for insertion into small incisions or for effective attachment to cervical vertebrae. In addition, current plates frequently lack the stability required to permanently orient the lamina in an appropriate position. Also, the design of existing laminoplasty plates often makes the process of attaching the plate to the vertebra and lamina very challenging. Finally, many existing laminoplasty plates are not adequately constructed to allow for conjunctive use of bone fusion material. Existing plates are also cumbersome for use with less invasive surgical procedures.
Accordingly, it remains desirable in the pertinent art to provide laminoplasty plates to address the limitations associated with known plates, including but not limited to those limitations discussed above. Additionally, it is desirable in the pertinent art to provide methods and systems for using the said laminoplasty plates to address the limitations associated with known methods and systems, including but not limited to those limitations discussed above.